Vietnam's leading partly private lenders, Eximbank and Sacombank, said on Tuesday they will consider merging as part of a cooperation plan, sparking high-volume trade in their shares which both closed higher on the day.

The two banks, both based in Ho Chi Minh City, plan to merge in the next three to five years and will seek approval for the merger from shareholders and government agencies, Eximbank said in a statement.

Vietnam's banking system, which has been hit hard by non-performing loans, has long been awaiting a consolidation of weak lenders. The country's central bank wants to reform nine lenders via mergers as part of a restructuring process started in 2011.

Eximbank and Sacombank are not among the nine lenders involved in the consolidation plan.

The two banks would sign a five-year cooperation plan in which they will support each other in lending, interbank activities, payments and in other areas, Eximbank said.

"This is the biggest merger deal so far, which will also draw interest from foreign investors," said Vu Duy Khanh, head analyst at Navibank Securities.